Vehicle occupant restraining systems are known in the art. Such systems include an air bag and a crash sensor for detecting the occurrence of a vehicle crash condition requiring deployment of the air bag. Upon the occurrence of a vehicle crash condition requiring deployment of the air bag, the crash sensor provides an electrical signal indicative of the crash condition. A crash sensor in a restraining system may be an actuatable switch, an inertia switch, and/or an accelerometer.
When the crash sensor provides the electrical signal indicative of the occurrence of a vehicle crash condition requiring deployment of an air bag, an electric current of predetermined magnitude and duration is passed through a squib, i.e., an electrically actuatable igniter, for the purpose of igniting the squib. The squib, when ignited, actuates a source of inflation fluid to direct inflation fluid into the air bag which results in inflation of the air bag.
Actuatable vehicle occupant knee blocker restraining systems are also known in the art. An occupant knee blocker is located at the lower portion of the vehicle's instrument panel and is movable from a stored position to an operative, knee blocking position in response to detection of a vehicle crash condition. Knee blocker restraining systems have been developed that combine an inflatable occupant air bag with a knee blocker. One such combined air bag and knee blocker restraining system is disclosed in U.S. Pat. No. 4,948,168.